1. Field of the Invention
The present invention relates generally to a filtration apparatus for separating solid particles from a liquid. More particularly, the invention relates to filtration apparatus for removing particulate contaminants from commercial laundry wastewater and to methods for accomplishing the same.
2. State of the Art
State and local governments across the country as well as the federal government have enacted new laws or expanded existing laws to reverse or limit the threat of environmental pollution. These environmental laws are typically directed toward commercial enterprises which create various wastes streams as a by-product of manufacturing products or providing services. The commercial laundry industry and particularly commercial Laundromats are specifically affected by environmental laws which limit the amount of suspended solids or particulate contaminants in commercial laundry wastewater which can be discharged into the environment. Particulate contaminants in commercial laundry wastewater generally consist of lint, hair, dirt and soap scum. To meet the requirements of current environmental laws, the amount of particulate contaminants in commercial laundry wastewater must be reduced to an acceptable level before it is discharged into the ground water and/or municipal sewage system.
Co-owned U.S. Pat. No. 5,350,526 discloses a filtration apparatus specifically intended for removing particulate contaminants from commercial laundry wastewater. It has at least one porous mesh-like filter bag coupled between an inlet manifold for receiving wastewater containing particulate contaminants and an outlet manifold for discharging the particulate contaminants separated from the wastewater. The filter bag is agitated by a paddle, so as to prevent the mesh-like material of the filter bag from being clogged. The apparatus is capable of trapping particles as small as 5 microns depending on the filter bag mesh. Those skilled in the art will appreciate that the finer the mesh the more slowly the water will be filtered. One of the challenges in designing a filter for commercial laundry wastewater is to be able to accommodate a flow rate of about 12,500 gallons per day.
Co-owned U.S. Pat. No. 5,575,913 discloses a filtration apparatus having a housing, a filter element, an inlet, a first discharge outlet and a second discharge outlet. The housing includes a bottom and an upwardly extending surrounding wall. The filter element is disposed in the housing and spans the surrounding wall with the filter element spaced above the bottom of the housing to define an upper chamber and a lower chamber, and the filter element being angled, preferably 45 degrees from the horizontal, so that one end of the filter element is lower relative to the other end. The inlet is in fluid communication with the upper chamber for receiving wastewater containing particulate contaminants. A first discharge outlet is in fluid communication with the lower chamber for discharging filtered wastewater. The second discharge outlet is in fluid communication with the upper chamber adjacent the lower end of the filter element for discharging filtered particulate contaminants. The apparatus is capable of trapping particles about 50 microns in diameter (or smaller, i.e. 5-10 microns).
The previously incorporated parent application discloses a filtration apparatus which includes a rectangular tank having an upper baffle and a lower baffle, layers of stone and carbon between the baffles, a water inlet above the upper baffle, and a water outlet below the lower baffle. The filtration apparatus is preferably used in conjunction with other apparatus including additional filters, holding tanks, a backwash pump and air blower, and a leaching pool system. The preferred implementation includes a laundry waste sump, a primary 50 micron static screen filter, an array of 100 micron filter socks, a 9,000 gallon holding tank, a pair of 100 gallon surge tanks, a pair of parallel secondary carbon filters according to the invention, a 5 micron polishing filter, a backwash pump, an air blower, a 6,000 gallon sludge holding tank, and a system of four leaching pools. According to the preferred methods, the carbon filters are operated for fourteen hours continuously and backwashed for ten minutes every day. Each carbon filter operates at a flow rate of approximately 9,000 gallons per day and is backwashed with 450 gallons of water.
The previously incorporated related application discloses a filtration apparatus which includes a filter element disposed at a 45 degree angle defining an upper chamber for solids and a lower chamber for liquid. A trough is disposed at the lower end of the filter element. The floor of the trough funnels toward a central drain and an overflow drain is located approximately 8 inches above the trough floor. The lower chamber is provided with a drain for recirculating water to a sprayer above the filter element and is also provided with an overflow drain approximately 8 inches above the floor.